Many networks such as local and wide area networks (LAN/WAN) structures are used to carry and distribute data communication signals between devices. The various network elements include hubs, switches, routers, and bridges, peripheral devices, such as, but not limited to, printers, data servers, desktop personal computers (PCs), portable PCs and personal data assistants (PDAs) equipped with network interface cards. All these devices that connect to the network structure require power in order to operate. The power of these devices may be supplied by either an internal or an external power supply such as batteries or an AC power via a connection to an electrical outlet.
Some network solutions offer to distribute power over the network in addition to data communications. The distribution of power over a network consolidates power and data communications over a single network connection to reduce the costs of installation, ensures power to key network elements in the event of a traditional power failure, and reduces the number of required power cables, AC to DC adapters, and/or AC power supplies which create fire and physical hazards. Additionally, power distributed over a network such as an Ethernet network may provide an uninterruptible power supply (UPS) to key components or devices that normally would require a dedicated UPS.
Additionally, the growth of network appliances, such as but not limited to, voice over IP (VOIP) telephones require power. When compared to their traditional counterparts, these network appliances require an additional power feed. One drawback of VOIP telephony is that in the event of a power failure, the ability to contact to emergency services via an independently powered telephone is removed. The ability to distribute power to network appliances or key circuits would allow network appliances, such as the VOIP telephone, to operate in a similar fashion to the ordinary analog telephone network currently in use.
The distribution of power over Ethernet network connections is in part governed by the IEEE Standard 802.3 and other relevant standards. These standards are incorporated by reference. However, these power distribution schemes within a network environment typically require cumbersome, real estate intensive, magnetic transformers. Additionally, power over Ethernet (PoE) requirements under 802.3 are quite stringent and often limit the allowable power.
There are many limitations associated with using these magnetic transformers. Transformer core saturation can limit the current that can be sent to a power device (PD). This may further limit the performance of the communication channel. The cost and board space associated with the transformer comprise approximately 10 percent of printed circuit board (PCB) space within a modern switch. Additionally, failures associated with transformers often account for a significant number of field returns. The magnetic fields associated with the transformers can result in lower electromagnetic interference (EMI) performance.
However, magnetic transformers also perform several important functions such as providing DC isolation and signal transfer in network systems.
Additionally there are many power losses associated with feeding power to the PD. One particular loss is the insertion loss that can vary with the data rate and transmission lines. Minimizing these losses allows the power fed to the PD to be maximized. Thus, there is a need for an improved approach to distributing power in a network environment that addresses limitations imposed by magnetic transformers while maintaining the benefits thereof.